The huge global scale of female genital mutilation has been revealed in disturbing new statistics, which show at least 200 million girls and women alive today have undergone ritual cutting, half of them living in just three countries.

The latest worldwide figures, compiled by Unicef, include nearly 70 million more girls and women than estimated in 2014 because of a raft of new data collected in Indonesia, one of the countries where FGM is most prevalent despite the practice being banned since 2006.

In the analysis of 30 countries, published to mark the International Day of Zero Tolerance for FGM, statistics showed women in Indonesia, Egypt and Ethiopia account for half of all FGM victims worldwide. Somalia has the highest prevalence of women and girls who have been cut – 98% of the female population between the ages of 15 and 49.

Claudia Cappa, the report’s lead author, said data from Indonesia shows FGM was practised more widely than researchers thought. “In countries where data was not available, we had previously only had anecdotal evidence. We knew Indonesia has a growing population of women and girls, but I would say (these figures) are higher than expected,” she said. “It shows it is a global issue, when the focus has previously been on Africa.”

About 44 million victims of FGM around the world are aged 14 or younger, and the majority of girls who have had their genitals mutilated were cut before they were five years old, Unicef’s research found.

In Guinea, where 97% of girls aged 15 to 49 are FGM victims despite the practice being outlawed, Unicef staff described seeing girls taken away from their families against their will to be cut, on the orders of village authorities. One five-year-old died from her wounds.

“Two days after this Christian community celebrated Christmas in a village, five-year-old Koumba was among 11 girls that were taken into the bush, some without their parents’ permission or knowledge, and others directly against strong parental protest, to receive their ‘initiation’,” the charity’s report said. “One day later, Koumba had bled to death before she could receive medical treatment.”

Unicef said the picture was optimistic in some countries, with FGM prevalence rates declining by 41% in Liberia, 31% in Burkina Faso, 30% in Kenya and 27% in Egypt over the last 30 years.

But in real terms numbers are still rising, largely due to population growth, and if trends continue the number of girls and women suffering genital mutilation will increase significantly over the next 15 years, Unicef said.

More young women are starting to speak out against the practice. Effie, a 20-year-old Malay-Muslim, told the Guardian she felt a creeping sense of horror as she read about genital mutilation on the internet, with the realisation the procedure she saw described as a backwards cultural practice had in fact been done to her when she was too young to realise.

“When I was growing up, around eight or nine, and was starting to get curious about how bodies worked, it came as a shock to find out that my body wasn’t the same as it was when I was born because of a medical procedure carried out without my consent or knowledge,” she said.

“Mainstream discussion on the issue fell into a very clear dichotomy that painted cultures that practised FGM as backwards or cruel. These were the kinds of discussions I read on the internet, and it further compounded the horror I felt in coming to terms with my own body.”

Effie said she still believed her family, whom she described as middle class and educated but traditional, had seen cutting as a religious obligation. It is the minds of her peers, not the older generation, that she is more focused on changing.

“Outlawing the practice will [go] a long way, and that requires political representatives to listen to their citizens instead of shutting down discussion, but I also believe there should be an accompanying change in mindset via awareness campaigns and community engagement, because legal reform can only go so far in discontinuing a practice so ingrained in our culture,” she said.

Cappa said the struggle to change attitudes faster than population growth was extremely difficult to square with the inclusion of a target to eliminate FGM by 2030 in the UN’s new sustainable development goals.

“The risk of being subjected to the practice is going down, because of changing attitudes, but the numbers are increasing because the global population is rising.

“That makes elimination even more challenging and current efforts are not sufficient to combat this growth. FGM is happening in every continent, especially with the migration of people from traditional communities into other countries.”

In England, the government’s health statistics body found 2,421 mutilation cases were reported to health authorities between April 2015 and September 2015. Campaign group Equality Now called the numbers “the tip of the iceberg” and said it estimated about 137,000 women and girls in England and Wales have been cut, calling for better teacher training on how to spot girls at risk.

• This article was amended on 8 February 2015 to correct the figure and time frame for the number of female genital mutilation cases reported to health authorities in England.